Electro-mechanical counter



Maz-zh l, 1966 R. E. EINEM ETAL 3,238,359

- ELECTRO-MECHANICAL COUNTER Filed May 16, 1963 3 Sheets-Sheet l om mvo. C

NQ .v0 da Od Nr Ob z l .March l, 1966 R. E. EINEM ETAL 3,238,359

ELECTRO-MECHANICAL COUNTER Filed May 16, 1963 5 Sheets-Sheet 2 413:8 H2 lb ab INVENTORS Rasee-r E.. ENEM ENNO Kruep BY A ATTORNEY March 1, 1966 R. E YEINEM ETAL ELECTRO-MECHANICAL COUNTER 3 Sheets-Sheet 3 Filed May 16, 1963 IN V EN TORS Roseau' E. Emam ENNo A- KNEF ATTORNEY United States Patent O 3,238,359 ELECTR-MECHANICAL COUNTER Robert E. Einem, Emmet Township, Dodge County, and

Enno A. Knief, Watertown, Wis., assignors to Eurant Manufacturing Co., Milwaukee, Wis., a corporation of Wisconsin Filed May 16, 1963, Ser. No. 289,786 8 Claims. (Cl. 23592) This invention pertains to improved high speed electromechanical counters of the type adapted to count the number of input pulses and to indicate such number by visual and/ or electrical readout means.

Further, this invention relates to counters which incorporate circuitry by means of which a transfer or output pulse is produced after the reception of a predetermined number of consecutive input pulses. This feature renders the counters particularly adaptable for stacking whereby the transfer pulse of each counter constitutes the input pulse of the next successive counter of the stack, and wherein the stack is capable of indicating any number whose digits are equal to the number f individual counters in the stack.

The basic components of counters of this type are a number wheel, an electrically actuated stepping mechanism, and switching circuitry for the production of the transfer pulse as well as for the resetting of the number wheel to its initial starting or zero position. To permit the stacking of the counters so that their visual readout means portray a single multi-digit number, the counters have to be of a fairly compact design. To meet this requirement, some counters of the prior .art provided printed transfer pulse and reset circuits on the side panels of the counter housing, lwhich circuits were wiped by wiper blades mounted on the number wheel. However, these counters have not been perfected to the point Where their life is comparable to that of the industrial equipment with which they are generally used. The primary trouble has been the rapid breakdown and wear of their electrical components.

The principal object of this invention is to provide an improved electro-mechanical counter which will be more eicient and which will have a substantially longer service life than similar counters known heretofore.

The novelty of this invention lies in a new stepping mechanism design which permits switching in the counter circuitry during times when the circuitry is de-energized.

Further the novelty of this invention lies in the particu lar construction of the stepping mechanism and of the switching components which construction will be more fully understood from the detailed description found in the specication.

The basic components of a counter embodying the present invention are a number wheel, a stepping mechanism having a ratchet wheel and an electro-magnet actuated drive pawl, and printed circuitry which is swept by a wiper blade carried by the number wheel. The electromagnet and the printed circuitry are energized during the reception of an input pulse by the counter and are deenergized during the time interval between the input pulses. The design of the stepper mechanism is such that the pawl is cocked during the application of voltage to the electro-magnet and only engages and advances the ratchet wheel and thus the number wheel after the voltage in the electro-magnet drops to zero. The novel result of such stepping action is that the wiper blade moves between the various contacts of the printed circuitry only during times when the printed circuitry is de-energized. Therefore, current is not switched by the wiper blades, since the motion of the wiper blades does not occur when the printed circuits are energized, but only occurs after the Patented Mar. 1, 1966v pulse voltage has dropped to zero. This switching feature is possible because of the drive principle of the stepping mechanism. Since current is not switched byY the wiper blades, the life of the printed circuit and the contacts is vastly increased and a weakness inherent in most similar devices known heretofore is eliminated.

In View of the above, a further object of this invention is to provide a counter having a stepping mechanism which functions to permit switching in the circuitry of the counter only during times when the counter circuits are de-energized.

Further, it is within the contemplation of this invention to provide an electrical readout circuit which broadly comprises a wiper blade mounted for rotation with the ratchet wheel and adapted to sweep a printed circuit in which the wiper blade makes a contact between a common or buss conductor (pad) and separate number pads. The readout provides a different electrical connection for each setting of the number wheel.

In order to provide .an increased life for the printed circuit of the readout, the wiper blade, having two contacts, is eccentrically mounted on the ratchet wheel thereby providing two separate paths over the printed circuit. As compared to prior counters of similar type, this feature doubles the life of the printed circuit. Further the ratchet wheel is geared to provide two rotations to the number wheel per one rotation of the ratchet wheel. Because of this, each contact of the wiper blade contacts the number pads and buss pad only once per two revolutions of the counter, thereby again increasing the life of the printed circuit by a factor of two. Thus, it is seen that the com-v bination of the eccentric mounting and the 2:1 ratio increases the life of the printed circuit by a factor of four.

In View of the above a lfurther important object of this invention is to provide a counter having a readout circuit of significantly increased service life.

Other objects and advantages will be pointed out in,

or be apparent from, the specification and claims, as will obvious modications of the single embodiment shown in the drawings, in which:

FIG. 1 is a plan View of the stepping mechanism and the number wheel of a counter embodying the present invention, the parts being mounted to one of the two side panels of the counter housing,

FIG. 2 is a side view of the structure shown in FIG. 1 with the other side panel being operably positioned over the stepping mechanism so as to provide a contact between the wiper blades of the mechanism and the number wheel and the printed circuitry carried on the inside face of the other side panel,

FIG. 3 is a fractional plan view similar to FIG. 1 showing the pawl of the stepping mechanism in a cocked position,

FIG. 4 is a plan view of the side panel which carries the printed circuitry showing the wiper blades in broken lines superimposed thereon and in a position when the counter provides a zero readout,

FIG. 5 is a View taken on line 5 5 of FIG. 1 and showing the armature plate in cross section,

FIG. 6 is a View taken on line 6 6 of FIG. 5,

FIG. 7 is a detail view of the ratchet wheel wiper blade.

FIG. 8 is a fragmentary front view of the counter,

FIG. 9 is a detail View of the yoke spring,

FIG. 10 illustrates the yoke spring action showing the yoke spring in an exaggerated tilted position, and

FIG. 11 is a perspective view of a stack of counters assembled in a unit capable of indicating a multi-digit number.

The counter embodying the present invention is contained within a housing 10, which is comprised of a rectangular frame 12 and side panels 14 and 16, the latter being removably secured to each other and to the frame by means of screws 18 passing through one side panel and engaging internally threaded bushings 20 of the other side panel. The frame and side panels form an elongated closed structure which may be easily assembled in a stack, as shown in FIG. 1l, in which the readout windows 22 of the individual counters are sufficiently close to each other to portray an easily readable multi-digit number.

Side panel 14 is of a nonmagnetic material and carries the stepping mechanism 23 and the number wheel 24. Side panel 16 is of a dielectric material and carries on its inside surface a printed reset circuit 26 (circuit 26 being, however, used for two purposes, for resetting and for providing an output pulse) and a printed readout circuit 28. The former circuit is wiped by contacts 30 and 31 of the resilient wiper blade 32 which is carried by the number wheel and the latter circuit is wiped by contacts 34 and 35 of the resilient wiper blade 36 carried by the ratchet lwheel of the stepping mechanism.

The stepping mechanism The stepping mechanism is actuated in response to the application of input pulse voltage to the electro-magnet 42 and is adapted to advance the ratchet wheel 40 and the number wheel 24 after the voltage in the electro-magnet has dropped to zero. The electro-magnet is comprised of a U-shaped laminated core 44 and coils 46 which are connected in series and which have a positive lead 48 and a negative lead 5U adapted to be connected in an external circuit (not shown) which produces the input pulses to be counted. Thus voltage is applied to the electro-magnet during the reception of the input pulses and drops to zero during the time intervals between the input pulses. The electro-magnet is mounted on the side panel 14 by means of screws 52.

The number wheel 24 is rotatably carried on a stub shaft S4 by means of a hub 56. The hub has a transversely extending and raised portion 58 located on one side of the top Isurface of the hub and engaging a slot 60 of the wiper blade 32. As best seen in FIG. 1, this type of mounting locates contact 31 closer to the center of rotation of the wiper blade than contact 30, thereby causing the contacts to travel in concentric paths of different diameters during rotation of the number wheel. A desirable feature of the above described mounting means is that it permits the use of a symmetrical wiper blade. The symmetry significantly simplifies the blades manufacture and its assembly in the counter. Further the symmetry assures that both contacts are biased with equal pressure against the printed circuit of panel 16.

The number wheel is mounted for rotation with the ratchet wheel 40 by means of engaging gears 62 and 64 which are integral with their respective wheels. The number wheel is geared to the ratchet wheel at a 2:1 ratio, such that one-half revolution of the ratchet wheel will equal one revolution of the number wheel. The ratchet wheel is rotatably mounted on stub shaft 66 by a hub 68. The hub also contains a raised portion 70 which engages slot 72 in the ratchet wheel wiper blade 36 to thereby provide dilerent concentric paths for the wiper blade contacts 34 and 35. As it is apparent, the mounting method is identical to that of the number wheel wiper blade, thus providing the same advantageous feature gained by the use of a symmetrical blade. Further this feature increases the life of the printed circuit by a factor of two.

The tit between the slots 60 and 72 and the corresponding raised portions 58 and 70 is such that the wiper blades may be easily lifted olf their respective hubs when it is desired to replace them or to remove them for some other purpose. When the housing is assembled, side panel 16 slightly depresses the outer ends of the wiper blades, thus creating a biased contact between the blades 4 and the printed circuitry of the panel. The tit between the wiper blades and the raised portions permits the blades to rock (prior to mounting of the panel) thereby permitting the blades to adjust themselves to provide equal bias against the side panel 16 when the latter is secured to the housing.

The ratchet teeth 74 are engaged by a drive pawl 76', which is pivotally secured to a drive arm 78 by means of a pin 89 and which is biased against the ratchet wheel by a spring 82. The drive arm is pivotally secured to the side panel by a drive arm pivot 84. An armature plate 86 is pivotally connected to the drive arm by a bracket 88 and a pin 90. The bottom face of the armature plate is provided with a mylar lm 87 which serves to space the armature plate from the cores 44 to thereby relieve the residual magnetism of the armature.

Upon reception of an input pulse by the counter, the input pulse voltage is applied to the coils 46 causing the armature plate 86 to be pulled against the magnetic cores 44 of the electro-magnet. The downward pull of the armature causes the drive arm 78 to pivot in a counterclockwise direction around pin 84 (as seen in FIG. 1), thereby causing the boss 92 of the dri've pawl 76 to slide backwardly over ratchet tooth 741 and assume the position as shown in FIG. 3. During this motion of the pawl, the ratchet is restrained from backward movement by a hairspring 94. The mechanism remains in this cocked position throughout the application of the input pulse voltage to the electro-magnet 42. As the voltage in the electro-magnet drops to zero (at the end of the input pulse), the armature 86 is released and the drive arm is caused to travel upwardly and in a clockwise direction around pin 84 in response to the bias of yoke spring 96 which engages the armature bracket 88K and the two yoke spring cams 98. During this motion the boss 92 engages the ratchet tooth 741 and advances the ratchet wheel by 18 thereby causing a travel of 36 by the number wheel. This travel, of course, causes the number wheel to expose a higher numeral through the readout window 22 than prior to its actuation.

The drive pawl is provided with two bosses, 92 and 100, which cooperate to perform the function usually accomplished by use of two separate pawls, i.e., to limit the advancement of the ratchet to one predetermined step. The cooperation is as follows: upon release of the armature from the electro-magnet the boss 92 is moved to engage the ratchet tooth 741 and thereby advance the ratchet wheel, and the boss is simultaneously moved to engage the top face of another one of the ratchet teeth thereby preventing motion of the ratchet wheel relative to the pawl. When the armature cornes to rest in the free position shown in FIG. l, any further forward motion of the ratchet wheel (as caused by inertia or some external force) is prevented by boss 100. This cooperation, of course, insures that the wheels only travel the intended increment per input pulse.

It is important to note that the location of the boss 100 is such that the force which would be exerted thereon, if the ratchet wheel were attempted to be rotated without the actuation of the armature 86, will tend to press boss 92 into together engagement with the wheel.

Further, this force will be in such a direction that it will not have a component (or component of sutilcient magnitude) in a direction (counterclockwise in FIG. l) around pin 84 which would aid in pivoting the drive arm 78 away from the ratchet wheel. In fact, the illustrated embodiment shows the boss 100 so located that the turning force of the ratchet will be in a direction tending to pivot drive arm 78 yet closer to the wheel.

An important part of the stepping mechanism design is the biasing means incorporated therein. The biasing means comprise the yoke spring 96 and a preload spring 102, both springs being operable to resist the downward movement of the armature in response to the voltage applied to the coils of the electromagnet and also, of course, operable to move the armature away from the cores 44 and to impart motion to the drive arm and paWl to thereby advance the ratchet wheel. The preload spring is secured to the drive arm 78 and contacts cam 104. Cam 104 and cams 98 are eccentrics which may be rotated to vary the bias of their respective springs.

The preload of the armature is determined both by the position of cams 98 in respect to the yoke spring 96 and by the position of cam 104 in respect to the preload spring 102. Cams 98 provide the rough adjustment and cam 104 provides the ne adjustment. The advantages of providing the preload spring 102 are twofold; irst the ne adjustment requires the manipulation of only a single cam, and second the preload spring permits the use of a lighter and therefore more accurate yoke spring.

It is of note that the -distance between cam 104 and the drive arm pivot 84 is substantially greater than the distance between the pivot 84 and the pin 90. In the illustrated embodiment the ratio of the distances is approximately 5:1. The significance of this mechanical ad- Vantage is that the preload spring 102 performs the work equivalent to a spring positioned as the yoke spring 96 (essentially having no mechanical advantage) yet only has one-fth (at ratio 5:1) of the spring force of such equivalent spring. This feature thus also permits the use of a lighter and therefore more easily adjustable spring.

The yoke spring 96 is of a design which insures parallel motion (to faces of cores 44) of the armature plate 86 as it is pulled towards the cores 44 of the electro-magnet. Such motion is very desirable since variance in the time between the seating of the armature on one core `and the other would cause a serious rubbing of the contact face of the .armature and result in its accelerated wear. Although in assembling of counters of this type, the cores 44 are placed equally distant from the armature 86, unequal mag netic forces caused by normal variations in the coils or in the air gap spacings will tend to pull one side of the armature ahead of the other side. The yoke spring has been designed to counteract this unequality in force. This counteraction is `attained by the particular angulation of the yoke spring 96. As best seen in FIG. 9, the contour ofthe spring is somewhat bird-shaped, having two upwardly inclined portions S which engage the armature bracket 88, and having two downwardly inclined shorter end portions 110 which contact and exert a bias against the yoke spring cams 9S. Each spring end 110 is generally in aline which points towards the armature pin 90. In order to prevent one end of the armature plate from moving faster towards the electro-magnet than the other end, the yoke spring 96 is of a design which responds to any pivotal motion of the armature around pin 90 (which would necessarily result when one end travels faster than the other) to decrease 4the spring bias exerted on the slower travelling side of the armature plate and to increase the bias on the faster travelling side. The result of decreasing the bias on the slower side is that correspondingly less force is required to advance that side of the armature towards its core and thereby the weaker core of the electromagnet is able to pull the armature at the same speed as the stronger side. The principle is illustrated in the exaggerated example shown in FIG. 10. In this example the right hand coil is shown as exerting a smaller magnetic force than the left hand coil and, therefore, causing the left hand side to advance further (faster) towards the left coil. This disparity in travel has caused the armature bracket 88 to pivot around pin 90, thereby causing the right spring end 1101 to lift oli its cam, and thus necessarily otter less resistance than the left hand spring end 11011. In turn the left hand spring end is forced against the left cam 98, thereby causing a correspon in the resistance offered to the left end of the .t plate which results in slowing down of this side 0 armature. it should be understood that in practice l spring ends do not move away that the spring ends automatically adjust themselves so that the motion of the armature on the stronger coil side will be resisted by an increased spring bias and the motion on the weak coil side will be resisted by a de, creased bias, thereby permitting both ends of the armature to travel at the same speed towards the cores despite the disparity in magnetic forces between the two coils. By inclining the spring ends in a direction generally pointing towards the pin 90, the pivotal motion of the armature will also cause an equal angular movement of the spring ends in respect to the armature and thus assure maximum response to the disparity in magnetic forces.

Circutry The printed circuitry of the counter is illustrated in FIG. 4, showing a plan view of the inside surface of side panel 16 and the position of the number wheel wiper blade, and the ratchet wheel wiper blade in broken lines and corresponding to their positions shown in FIGS. l and 3. The

panel carries two separate circuits, a reset circuit 26 which is engaged by the number wheel Wiper blade 32, and readout circuit 28 which is engaged by the ratchet wheel wiper blade 36. The paths of the contacts 30, 31, 34, and 35 are shown by broken lines 301, 311, 341, and 351 respectively. -Positive and negative terminals 112 and 114 are connected to leads 48 and 50 of the electro-magnet and are connected Within the external circuit (not shown) generating the input pulses for the counter.

Both wiper blades are shown in a position which they assumed when the number wheel displays the number zero in the readout window 22. ln reference to FIG. 4, the number wheel wiper blade travels in a clockwise direction as the stepping mechanism is actuated, and the ratchet wheel wiper blade travels in a counterclockwise direction. The reset circuit has a dual purpose, one of its purposes is to transmit an output pulse after ten consecutive input pulses have been received when the counter has been started in the initial zero position, and the second purpose is to reset the counter to the zero position when it is desired to start a new count from that position.

As illustrated, the reset circuit is comprised of three components, `a reset pad 116 which is engaged by contact 30 when the number wheel is in any of the positions between 1 and 8 inclusive, a transfer pad v118 which is engaged by contact 30 when the number wheel is in the number 9 position, and a zero pad which is engaged by contact 30 when the reset wheel is in the zero position and which is continually wiped by contact 31. The zero pad is connected :to terminal 114 and thus has input pulse voltage applied to it when the pulse is received by the counter. The transfer pad 118 is connected to the positive terminal of the next decade of counters when the counter is used in a stacked assembly, or is connected to some other electrical circuit to which a signal has to be transmitted when the number wheel reaches the zero position. The reset pad is connected to a reset circuit which will be explained in detail hereafter.

During counting, the reset pad is externally disconnected and therefore the contact established between the zero pad 120 and the reset pad 116 when the number wheel moves between the positions of 1 and 8 has no effect upon the operation of the counter. After the ninth pulse has been received (i.e., after the ninth pulse voltage has dropped to zero), the contact 30 is moved to the transfer pad 11S. As the tenth pulse is received, the wiper blade 32 remains in the position establishing contact between the zero pad and the transfer pad 11S and transmits the tenth input pulse through conductor 122 to the next decade of a stack or to another desirable circuit. It should be appreciated that since contact 30 had from the cams, but only engaged the transfer pad 118 prior to the reception of "-e .entn input pulse, this input pulse is fed simultane- `ttsiy to the illustrated counter as well as the second decade of a stacked assembly or another circuit. This principle would also produce a simultaneous transfer pulse to the second as well as to the third, fourth, and other decades if the counters in those decades are set in the 9 position; as for example, in a stack of four counters indicating the number 0999, the thousandths pulse will be simultaneously fed to all four counters. Further, it should be appreciated that the transfer of the pulse is not affected by the timing of any internal mechanism or switching, since the number Wheel and wiper blade do not advance until a count pulse is completed. After the voltage of the tenth input pulse drops to zero, the Wiper blade is advanced to the shunting position as seen in FIG. 4. It should be noted that the advance made by contact 30 between any of the three circuit elements (116, 118, and 120) is always made when the zero pad is at zero potential and, therefore, any switching of curf rent is eliminated.

In order to reset the counter to the zero position, conductors 124 and 122 are connected to a source of either one-half wave sinusoidal or rectangular pulses which are carried through the wiper blade 32 to the zero pad 118 and thus to the electromagnet 42 to actuate the stepping mechanism. When the number wheel is in any position between 1 and 8, the reset pulse is carried through reset pad 116; when the number wheel is in the 9 position, the reset pulse is carried through the transfer pad 113. As the number wheel reaches the zero position during the resetting, contact 30 will engage the zero pad and thus interrupt the stepping action at this point. Also, in the resetting stage, wiper blade 32 does not switch current since it also is advanced only at times when the reset circuit is de-energized (between pulses).

The electrical readout circuit 28 is electrically isolated from the input pulse and reset circuits and is provided for the purpose of energizing a separate conductor at each of the ten number wheel settings, to thereby provide an electrical readout for the counter.

With the wiper blade 36 in the position shown in FIG. 4, the contact 34 engages the buss pad 126 and contact 35 is positioned on the zero readout pad 130. As the number wheel is advanced, Contact 34 will engage number one readout pad 131 and then successively readout pads 132 until it will have reached number 0 readout pad 130. As the number wheel is moved from the 0 to the number 1 position, Contact 34 will move to the buss pad 126 and contact 35 will engage number 1 pad 131. Because the ratchet wheel advance is only 180 for a full revolution of the number wheel, the travel of its wiper blade is correspondingly shorter and therefore tends to increase the service life of the printed circuit as well as of the wiper contacts. A further feature tending to increase the life of the printed circuitry is the off-center location of the wiper blade of the ratchet wheel, whereby two distinct paths of travel are provided for the respective contacts of the wiper blades, and correspondingly reduce the wear of the components.

The buss pad 126 may also be connected to the source of input pulses, in which case the electrical readout would be provided by means of an electrical pulse transferred to the readout pad which is engaged by the wiper blade contact 34 or 35 at the time of reception of the pulse. In this case the switching would be performed at times when the readout circuit 28 is de-energized. However, it should be noted that the electrical readout circuit may be connected to any desired external circuit, and for this reason the switching between the buss pad 126 and the ten readout pads would not necessarily occur at times when the readout circuit is de-energized. The additional Wear which will result if the readout is connected to a circuit which requires current switching is compensated by providing the two contact paths 541 and 351 on the buss pad as well as on the number pads, and the 2:1 ratio between the ratchet and number wheel.

To facilitate easy installation and connection of the above described counter, all electrical connections terminate on an extended portion 138 of side panel 16, thereby providing a plug-in member which may be engaged by suitable edge connectors.

Although the illustrated embodiment of the present invention contemplates the readout of the input pulses in the decimal system, it should be understood that the invention is not limited thereto but also encompasses the provision of read-out means based on a non-decimal system. It also should be understood that when reference is made to voltage in the specification and claims it is intended to refer to input pulse (or output pulse) voltage and not to any voltage which might be present in the coils due to residual currents therein.

Only one embodiment of the present invention has been illustrated and described, but it will be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the spirit of the invention or from the scope of the appended claims.

We claim:

1. An electro-mechanical counter adapted to count input pulses comprising,

electro-magnetic means for reception of the input pulses,

stepping mechanism operated by said electro-magnetic means,

a ratchet wheel driven by said stepping mechanism,

a large gear mounted on and movable with said ratchet Wheel,

a small gear engaged with and driven by said large gear,

a number Wheel mounted on and movable with said small gear,

a printed readout circuit in juxtaposition to said ratchet Wheel having a 360 printed circuit with a 180 bus pad and a plurality of spaced readout pads in the remainder of said 360 printed Acircuit equal in number to the number of input pulses required for one revolution of said number wheel, and

a wiper blade mounted on and carried by said ratchet wheel, said blade having diametrically spaced contacts with one contact engaging said bus pad and the other contact engaging said readout pads.

2. A counter according to claim 1 wherein said wiper blade contacts are spaced at different distances from the center of rotation of said Wiper blade thereby providing two separate paths over said printed circuit.

3. A counter according to claim 2 having a second printed circuit and a wiper blade carried for rotation by said number wheel.

4. An electro-mechanical counter adapted to be connected to a source of electrical input pulses and to indicate the number of received input pulses, comprising,

a wheel adapted to assume predetermined angular positions to thereby indicate the number of input pulses received by the counter and adapted to complete one revolution after the reception of n` input pulses,

a stepping mechanism connected to impart rotary movenent to said wheel,

electro-magnetic means operatively associated with said stepping mechanism to advance the same and connected to the source of input pulses and being adapted to have input pulse voltage applied to it,

an output circuit comprising, a first printed circuit conductor subjected to the input pulse voltage, a second printed circuit conductor subjected to input voltage after the reception of n-a input pulses Where a is any whole number, and a wiper blade connecting said two conductors to thereby subject said second conductor to the nth pulse voltage, and

a third prin-ted circuit conductor engaged by the said wiper blade when said wheel is in positions for re- 9 ceiving the second input pulse and any n-a input pulse.

5. A counter according to claim 4 wherein said Wiper blade is in a shunting position in respect to said rst conductor when said wheel is in a position to receive the first pulse.

6. In an electro-mechanical counter having an electromagnet connected to a source lof input pulses, a number Wheel, and a ratchet wheel having a pawl and being adapted to rotate said number wheel a predetermined distance, the combination of,

a printed circuit having a plurality of pads,

a wiper blade having two oppositely spaced contacts biased against said printed circuit and adapted to be moved in response to movement of one of said wheels, and

means mounting said wiper blade for eccentric rotation around an axis thereby providing two separate paths for said two contacts over said printed circuit. 7. A counter according to claim 6 wherein said means mounting said wiper blade allows limited rockable move- 5 ment of said blade thereby permitting even engagement of said wiper blade contacts with said printed circuit.

8. A counter according to claim 6 wherein said wiper blade is symmetrical in shape.

References Cited by the Examiner 15 DARYL W. COOK, Acting Primary Examiner.

MALCOLM A. MORRISON, Examiner.

I. F. MILLER, Assistant Examiner. 

1. AN ELECTRIC-MECHANICAL COUNTER ADAPTED TO COUNT INPUT PULSES COMPRISING, ELECTRO-MAGNETIC MEANS FOR RECEPTION OF THE INPUT PULSES, STEPPING MECHANISM OPERATED BY SAID ELECTRO-MAGNETIC MEANS, A RATCHET WHEEL DRIVEN BY SAID STEPPING MECHANISM, A LARGE GEAR MOUNTED ON AND MOVABLE WITH SAID RATCHET WHEEL, A SMALL GEAR ENGAGED WITH AND DRIVEN BY SAID LARGE GEAR, A NUMBER WHEEL MOUNTED ON AND MOVABLE WITH SAID SMALL GEAR, A PRINTED READOUT CIRCUIT IN JUXTAPOSITION TO SAID RATCHET WHEEL HAVING A 360* PRINTED CIRCUIT WITH A 180* BUS PAD AND A PLURALITY OF SPACED READOUT PADS IN THE REMAINDER OF SAID 360* PRINTED CIRCUIT EQUAL IN NUMBER TO THE NUMBER OF INPUT PULSES REQUIRED FOR ONE REVOLUTION OF SAID NUMBER WHEEL, AND A WIPER BLADE MOUNTED ON AND CARRIED BY SAID RATCHET WHEEL, SAID BLADE HAVING DIAMETRICALLY SPACED CONTACTS WITH ONE CONTACT ENGAGING SAID BUS PAD AND THE OTHER CONTACT ENGAGING SAID READOUT PADS. 